GLSL mode - Is that a bug?
The only way I can get anything like what you're seeing is to reduce the viewport's "clipping" END setting (press N and open the VIEW tab) to something below the START setting then approach the cube until this happens...  



Another point might be to ask where you downloaded Blender from?  I make a point of using the original/authoring site, never a third party site for any s/ware.

This is obvious I know but failing all else, you might also want to explore the possibility of it being a problem between Blender, the graphics card or it's drivers, or perhaps your operating system and/or it's version.  

I see your latest comment and note that you're using Win XP?  That's pretty old isn't it?  Blender has come a long way since the older versions of Windows.  Perhaps XP can't handle what Blender is doing re - shading etc.

When all else fails, look for the things it cannot possibly be!

EDIT:  I've since found out that XP is not supported by Blender versions beyond 2.76B